J band (infrared)
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In infrared astronomy, the J band refers to an atmospheric transmission window (1.1 to 1.4 μm) centred on 1.25 micrometres (in the near-infrared).
Betelgeuse is the brightest near-IR source in the sky with a J band magnitude of −2.99.{{cite web
|date=2009-09-07
|title=Very Bright Stars in the 2MASS Point Source Catalog (PSC)
|publisher=The Two Micron All Sky Survey at IPAC
|author=R. Cutri and M. Skrutskie
|url=http://www.ipac.caltech.edu/2mass/releases/allsky/doc/sec1_6b.html#satr1
|accessdate=2011-12-28}} The next brightest stars in the J band are Antares (−2.7), R Doradus (−2.6), Arcturus (−2.2), and Aldebaran (−2.1).{{cite web
|title=Simbad object query:Jmag<-2 & Vmag>-9
|publisher=SIMBAD Astronomical Database
|url=http://simbad.u-strasbg.fr/simbad/sim-sam?Criteria=Jmag%3c-2%20%26%20Vmag%3e-9&OutputMode=LIST
|accessdate=2012-08-22}} In the J band Sirius is the 9th brightest star.
The J band is a frequent source of ground based observations since the wavelengths it covers pass through clouds and other atmospheric gasses.{{Cite web |title=Infrared Astronomy Optical Filters |url=https://www.andovercorp.com/products/astronomy-filters/infrared-astronomy/ |access-date=2023-04-01 |website=www.andovercorp.com}} The waveband does however suffer from contamination by water vapor lines and hydroxide emission lines leading to relatively high photometric error.{{Cite journal |last1=Simons |first1=D. A. |last2=Tokunaga |first2=A. T. |date=February 2002 |title=The Mauna Kea Observatories Near-Infrared Filter Set. I: Defining Optimal 1-5 $\mu$m Bandpasses |journal=Publications of the Astronomical Society of the Pacific |volume=114 |issue=792 |pages=169–179 |doi=10.1086/338544 |arxiv=astro-ph/0110594 |s2cid=7880289 |issn=0004-6280}}
It can be used to scrutinize the photosphere of giant and supergiant stars while mostly avoiding opacities from molecular bands and also has access to the 1080 nm He I line which is useful in the study of circumstellar disk interactions around T-Tauri stars.{{Cite book |last1=Pedretti |first1=Ettore |last2=Piacentini |first2=S. |last3=Corrielli |first3=G. |last4=Osellame |first4=Roberto |last5=Minardi |first5=Stefano |title=Optical and Infrared Interferometry and Imaging VI |chapter=A six-apertures discrete beam combiners for J-band interferometry |editor-first1=Peter G. |editor-first2=Michelle J. |editor-first3=Antoine |editor-last1=Tuthill |editor-last2=Creech-Eakman |editor-last3=Mérand |date=2018-07-09 |chapter-url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10701/1070116/A-six-apertures-discrete-beam-combiners-for-J-band-interferometry/10.1117/12.2312033.full |publisher=SPIE |volume=10701 |pages=316–325 |doi=10.1117/12.2312033|arxiv=1809.01260 |bibcode=2018SPIE10701E..16P |isbn=9781510619555 |s2cid=119458175 }} J, H and K-band spectroscopy is also commonly used to observe and research brown dwarfs{{Cite journal |last1=Kirkpatrick |first1=J. Davy |last2=Cushing |first2=Michael C. |last3=Gelino |first3=Christopher R. |last4=Griffith |first4=Roger L. |last5=Skrutskie |first5=Michael F. |last6=Marsh |first6=Kenneth A. |last7=Wright |first7=Edward L. |last8=Mainzer |first8=A. |last9=Eisenhardt |first9=Peter R. |last10=McLean |first10=Ian S. |last11=Thompson |first11=Maggie A. |last12=Bauer |first12=James M. |last13=Benford |first13=Dominic J. |last14=Bridge |first14=Carrie R. |last15=Lake |first15=Sean E. |date=2011-12-01 |title=The First Hundred Brown Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE) |url=https://ui.adsabs.harvard.edu/abs/2011ApJS..197...19K |journal=The Astrophysical Journal Supplement Series |volume=197 |issue=2 |pages=19 |arxiv=1108.4677 |bibcode=2011ApJS..197...19K |doi=10.1088/0067-0049/197/2/19 |issn=0067-0049 |s2cid=16850733}} and directly imaged exoplanets.{{Cite journal |last=Oppenheimer |first=B. R. |year=2013 |title=Reconnaissance of the HR 8799 Exosolar System I: Near IR Spectroscopy |journal=The Astrophysical Journal |publisher=Cornell University |volume=768 |issue=1 |pages=24 |arxiv=1303.2627 |bibcode=2013ApJ...768...24O |doi=10.1088/0004-637X/768/1/24 |s2cid=7173368}}
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